Small Vessel Capable Of High Tow Force

ABSTRACT

A small watercraft with watertight hull and an area at the rear in close proximity to the waterline that provides a means to mount payloads. Engines powering propellers are installed forward of the payload area and are covered by a water-tight deck with openings for intake air. Ancillary systems to support the engines and electrical components are provided in a conventional manner. A feature of the present invention is that the hull has been modified to permit a tow cable to pass through the hull from a towing winch to a towed body. The present invention moves the reaction from the tow force forward of the craft transom and low in the hull which greatly improves the stability of the small vessel particularly when it is operating in rough water. The present invention is applicable to any size of the hull and any materials that the hull is fabricated from.

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

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REFERENCE TO SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

This invention relates generally to a watercraft which is used for towing objects at or below the surface of the water. The power to propel the craft through the water is the total of the resistance of pushing the hull through the water plus the tow force. The tow force exerted by conventional watercraft is small compared to the force required to push the hull through the water.

When the tow force is large compared to the force required to push the watercraft through the water, the location where the tow force is applied to the craft can cause the vessel to become unstable. Specific provisions are made to maintain the stability of the vessel. For example, commercial tugboats attach the tow cable as close to the center of gravity of the vessel as possible. The center of gravity is generally well forward of the transom and as low vertically as possible.

The limitation of conventional small watercraft for towing high forces is increased as the roughness of the water surface increases. This is because when the additional tow force is combined with the destabilizing forces of the waves, the craft becomes unstable and increases the potential to capsize.

The present invention provides a means to eliminate the tow force limitations of the small watercraft by maintaining the stability of the watercraft. The present invention also provides the means to simplify the implementation of deploying and recovering towed objects from the small watercraft. The present invention also provides the means for a watercraft to provide high tow forces when the angle of the tow cable is significantly below horizontal.

BRIEF SUMMARY OF THE INVENTION

A watercraft which includes a watertight hull, at least one propulsion engine, at least one drive shaft and propeller, fuel tank to provide energy for the engine(s), and a means to control the direction of the craft and the speed. The watercraft includes an deck area that is in close proximity to the surface of the water beginning at the transom of the craft and extending forward.

The hull is shaped to develop minimal resistance when moving through the water. There is a vertical slot formed through the hull at the transom along the centerline of the craft extending from the top of the aft deck area to the hull plating. The slot is positioned so that a tow cable can pass through the slot when the angle of the tow cable is below horizontal. Conventional winches and reels are utilized to deploy and recover the tow cable. Wear resistant material is attached to the lower and aft edges of the slot thru the hull to eliminate chafing between the cable and the watertight hull boundary.

When the watercraft is operating with the tow cable deployed, with calm seas, with no currents, and with a tow cable angle below horizontal the tow cable will extend through the slot in the hull. The force on the tow cable will exert both a longitudinal and a vertical force on the craft. The impact to the stability and resistance of the watercraft due to the tow forces is reduced in the present invention because it permits the forces on the tow cable to be reacted closer to the center of gravity of the watercraft.

When a cross current is added to the operating conditions above, the watercraft will need to operate at a angle, referred to as yaw angle, to the desired direction of motion to counteract the force of the current. The tow cable will still extend through the slot in the hull and exert both a longitudinal and a vertical force on the craft. However, due the yaw angle of the craft, the tow cable will be in contact with the lower edge of the slot through the hull which will exert a transverse force on the hull. The distance from the vertical center of gravity will be greatly reduced compared to the prior art where the tow cable goes over the side of the upper deck. The result is a significant reduction in the destabilizing moment imposed by the tow cable on the craft.

The slot through the hull is constructed in such a manner so that the stresses created in the craft structure due to the applied forces, by the water on the hull, by the tow cable, or by forces on the craft from hoisting, do not exceed the yield strength of the material used to construct that area of the craft. The inside surfaces of the edges of the slot through the hull are covered to prevent the tow cable from chaffing on the edge and to increase the bend radius of the tow cable as it passes the edge.

It is an object of this invention to provide a stable watercraft that has a high tow force compared to the force required to push the craft thorough the water.

It is another object of the present invention to provide a watercraft that has a high tow force compared to the force required to push the craft through the water with a slot through the hull so that the reaction of the force of the tow cable is reacted closer to the center of gravity.

It is still yet another object of this invention to provide a watercraft that has a high tow force compared to the force required to push the craft through the water with increased resistance to capsizing in high sea states.

In accordance with these and other objects that will be apparent hereinafter, the present invention will now be described with particular reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 Side view of the watercraft.

FIG. 2 Section view of the watercraft.

FIG. 3 Aft end view of the watercraft.

FIG. 4 Section view of aft portion of the watercraft.

FIG. 5 Section view of the watercraft with towed body deployed.

FIG. 6 Section view of the watercraft with towed body deeply deployed.

FIG. 7 Section view of the watercraft with towed body shallowly deployed.

FIG. 8 Section view of the watercraft with reel and towed body deeply deployed.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like characters designate like or corresponding parts throughout the several views. A semi-planning hull is shown in all of the implementations to simplify the figures. The present invention can be readily applied to other hull forms or shapes. FIG. 1 shows a side view of the watercraft 10 with payload mounting area 20 empty. The hull plating 12 is joined to the deck plating 14 to form a watertight boundary to prevent water from entering the craft in the event of a wave washing over the deck or the craft capsizing due to large wave impact. The design waterline is indicated by 30. The propellers 54 are recessed in tunnels 56 to protect them from damage due to impacting objects in the water.

FIG. 2 is a section view showing the arrangement of the major components. The engines 50 are located forward of the payload area as close to the hull plating as possible. The engine exhaust 51 discharges through the side of the hull. The drive shaft 52 connects the engine to the propeller 54. The propeller tunnels 56 begin forward of the propellers and expand gradually to prevent separation of the flow and to eliminate the resultant inefficiencies. A generic payload enclosure 30 is shown on the payload mounting area. A cable reel 32 is located at the forward end of the payload compartment and an A-frame gantry 34 is located at the aft end. The A-frame gantry is configured so that it can rotate forward and aft about the mounting bracket 36. A generic towed body 38 is shown in the stowed position on the deck of the payload compartment.

FIG. 3 is a view of the aft end of the watercraft in the same configuration as FIG. 2. The support cradle 39 for the towed body 38 allows the towed body to be raised vertically but constrains its motion side to side. The tow cable pulley 40 is aligned along the centerline of the towed body. Bumpers 41 are included on the A-frame 34 to prevent the towed body from hitting the side supports. A compliant means 43 is provided on either side of the pulley to press the towed body 38 against the support cradle 39. The A-frame 34 pivots about the mounting brackets 36. The propellers 54 are shown in tunnels 56 which are used to reduce the vulnerability of the propellers to damage. The rudders 58 are mounted behind the propellers to provide directional control of the craft. A slot 46, extending from the payload area through the keel to the lower hull plating 12, is also along the centerline. The slot 46 permits the tow cable to pass through the hull along the centerline of the craft.

FIG. 4 is a section view of the aft portion of the craft along the centerline. The slot 46 that extends from the payload area through the keel, is shown as extending forward from the transom and ending at the forward end of the A-frame when it is in the forward position. The length of the slot is dependent on the configuration of the watercraft and those skilled in the art of designing and building watercraft will make adjustments to apply the present inventions to their application. The structure of the watercraft with the slot through the hull is modified to provide the sane structural stiffness as a watercraft without the slot.

FIG. 5 is a section view of the watercraft 10 along the centerline with the towed body 38 deployed and operating at a shallow depth. The tow cable 42 remains engaged with the pulley 40 on the A-frame 34. In this orientation, the majority of the forces from the towed body are horizontal which are applied to the winch. FIG. 6 is similar to FIG. 5 except that the towed body 38 is now operating at a deeper depth which creates a steeper angle on the tow cable 42. The tow cable passes through the slot pivoting about the pulley on the A-frame. If the tow cable angle is considered to be 45 degrees, the forces on the tow cable are evenly split between horizontal and vertical. The vertical forces are reacted to the hull through the pulley and A-frame. Because the pulley is forward of the transom, the resulting moment on the watercraft due to the vertical force of the tow cable is less than the moment that would result from the cable pulling down over the transom. The horizontal force is transferred to the hull through the cable reel 32.

FIG. 7 is a section view of the watercraft 10 along the centerline with the towed body 38 deployed and operating at a shallow depth with the tow cable 42 supported by a rigid tow bar 48. The rigid tow bar is attached to the craft at a point 50 and extends beyond the aft edge of the craft. The location of the pivot point is determined by the body being towed, the geometry of the A-frame, and the loads on the tow cable. There is a feature at the outboard end of the rigid tow bar 49 that prevents the tow cable from making too small a radius bend. The forces applied to the hull are the same with the rigid tow bar as with the bare cable. FIG. 8 is similar to FIG. 7 except that the towed body 38 is now operating at a deeper depth which creates a steeper angle on the tow cable 42 and the rigid tow bar 48. The rigid tow bar passes through the slot in the hull pivoting about the attachment point 50.

Although illustrative embodiments of the present invention have been shown and described herein in what are considered to be the most practical and preferred embodiments. It is recognized however, that changes and modifications may be effected therein by those skilled in the art without departing form the scope or spirit of the invention. 

What I claim as my invention is:
 1. A watercraft that is constructed with conventional materials, powered by at least one internal combustion engine, moved forward through the water with a propulsor, that has a means to provide directional control, and has a longitudinal slot though the hull that extends vertically though the hull beginning at the transom and extending some distance forward of the transom.
 2. A watercraft as described in claim 1, wherein the perimeter of the slot though the hull is continuously open from the forward most point of the slot on the upper surface rearward to the top of the transom, down to the bottom of the transom and forward to the forward most point of the slot on the lower surface.
 3. A watercraft as described in claim 1, wherein structural support is provided around the slot though the hull so that the craft deflections due to forces imposed on it are similar to those of the craft without the slot.
 4. A watercraft as described in claim 1, that when used for towing, the tow cable can pass from the upper surface of the craft through the slot though the hull.
 5. A watercraft as described in claim 4, wherein structural support is provided around the slot though the hull so that the deflections of the edges of the slot due to forces imposed on it by the tow cable do not permanently deform the slot.
 6. A watercraft as described in claim 4, wherein the rear and lower edges of the slot though the hull are covered with anti-wear material to protect the craft structure and the tow cable from damage due to chaffing.
 7. A watercraft as described in claim 4, wherein the rear and lower edges of the slot though the hull are covered to increase the radius of the tow cable to prevent damage to the tow cable due to making too small of a radius around a sharp corner.
 8. A watercraft as described in claim 4, wherein the forces imposed by the tow cable are applied closer to the longitudinal center of gravity of the craft than they would have been if the slot though the hull were not present.
 9. A watercraft as described in claim 4, wherein the forces imposed by the tow cable are applied closer to the vertical center of gravity of the craft than they would have been if the slot though the hull were not present.
 10. A watercraft as described in claim 1, that when used for towing, a rigid tow bar can pass from the upper surface of the craft through the slot though the hull.
 11. A watercraft as described in claim 10, wherein structural support is provided around the slot though the hull so that the deflections of the edges of the slot due to forces imposed on it by the rigid tow bar do not permanently deform the slot.
 12. A watercraft as described in claim 10, wherein the rear and lower edges of the slot though the hull are covered with anti-wear material to protect the craft structure and the tow cable from damage due to chaffing.
 13. A watercraft as described in claim 10, wherein the end of the rigid tow bat has provisions to increase the radius of the tow cable to prevent damage to the tow cable due to making too small of a radius at the end of the rigid tow bar.
 14. A watercraft as described in claim 10, wherein the forces imposed by the rigid tow bar are applied closer to the longitudinal center of gravity of the craft than they would have been if the slot though the hull were not present.
 15. A watercraft as described in claim 10, wherein the forces imposed by the rigid tow bar are applied closer to the vertical center of gravity of the craft than they would have been if the slot though the hull were not present.
 16. A watercraft that is constructed with conventional materials, powered by at least one internal combustion engine, moved forward through the water with a propulsor, that has a means to provide directional control, and has a longitudinal slot through the hull that extends vertically though the hull beginning at the bow and extending some distance aft of the bow.
 17. A watercraft as described in claim 16, wherein the perimeter of the slot though the hull is continuously open from the forward most point of the slot on the upper surface rearward to the top of the rear transverse edge of the slot, down to the bottom of the transverse edge of the slot and forward to the forward most point of the slot on the lower surface of the hull.
 18. A watercraft as described in claim 16, wherein structural support is provided around the slot though the hull so that the craft deflections due to forces imposed on it are similar to those of the craft without the slot.
 19. A watercraft as described in claim 16, that when used for towing, the tow cable can pass from the upper surface of the craft through the slot though the hull.
 20. A watercraft as described in claim 19, wherein structural support is provided around the slot though the hull so that the deflections of the edges of the slot due to forces imposed on it by the tow cable do not permanently deform the slot.
 21. A watercraft as described in claim 19, wherein the rear and lower edges of the slot though the bull are covered with anti-wear material to protect the craft structure and the tow cable from damage due to chaffing.
 22. A watercraft as described in claim 19, wherein the rear and lower edges of the slot though the hull are covered to increase the radius of the tow cable to prevent damage to the tow cable due to making too small of a radius around a sharp corner.
 23. A watercraft as described in claim 19, wherein the forces imposed by the tow cable are applied closer to the longitudinal center of gravity of the craft than they would have been if the slot though the hull were not present.
 24. A watercraft as described in claim 19, wherein the forces imposed by the tow cable are applied closer to the vertical center of gravity of the craft than they would have been if the slot though the hull were not present.
 25. A watercraft as described in claim 16, that when used for towing, a rigid tow bar can pass from the upper surface of the craft through the slot though the hull.
 26. A watercraft as described in claim 25, wherein structural support is provided around the slot though the hull so that the deflections of the edges of the slot though the hull due to forces imposed on it by the rigid tow bar do not permanently deform the slot.
 27. A watercraft as described in claim 25, wherein the rear and lower edges of the slot though the hull are covered with anti-wear material to protect the craft structure and the rigid tow bar from damage due to chaffing.
 28. A watercraft as described in claim 25, wherein the end of the rigid tow bat has provisions to increase the radius of the tow cable to prevent damage to the tow cable due to making too small of a radius at the end of the rigid tow bar.
 29. A watercraft as described in claim 25, wherein the forces imposed by the rigid tow bar are applied closer to the longitudinal center of gravity of the craft than they would have been if the slot though the hull were not present.
 30. A watercraft as described in claim 25, wherein the forces imposed by the rigid tow bar are applied closer to the vertical center of gravity of the craft than they would have been if the slot though the hull were not present. 